Currently you can use the webpage Query String to compare against in both triggered and filtered flows, however it is the only filter aspect of the "Visits Web Page" or "Clicks Link" that cannot also be used as a token [technically "Browser" too; but there are other easier ways of getting that].
While its easy enough to get the query string parameters into invisible fields on a page with a form, there is a need to write this data to lead records sometimes on pages without forms. Currently, the work-around is to either create a completely invisible form capturing the data fields required, and have a JS that auto-submits the form, or to do some work with the Munchkin to write a "fake" visits web page that can be tokened.
However, these two work-arounds both have problems. Clearly creating an invisible form with an auto-submit not only increased page loading time and increases risk for loading errors, and the method with the munchkin logging ghost "web page visits" is limited only to looking for query string variables that you know you are looking for in advance.
Adding a {{trigger.Query String}} or expanding the token {{trigger.Web Page}} to include not just the page's base URL but the query string as well would allow for additional UTM tracking on pages without a form. Being able to write that data to a field, then either use a CRM or data export to parse it and return filtered data would greatly expand Marketo's ability to handle inbound data and increase lead trackability.
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